The correct answer is “at the beginning of the play, Ophelia is obedient and proper, but Polonius's death causes her to behave strangely and inappropriately”
Ophelia at the beginning of the play is very obedient and proper, this is because she is very dependent on the male authorities of her life. She represents the frailty of women at the time.
When Polonius dies and Hamlet is exiled to England she goes mad. All these events are too much pressure for her to handle.
Her madness plays a major role in her development during the play because it leads her to her suicide.